As-contaminated Drinking Water Research Articles

Natural Clay Minerals as Potential Arsenic Sorbents from Contaminated Groundwater: Equilibrium and Kinetic Studies

Arsenic (As) contaminated groundwater is a worldwide concern due to its chronic effects on human health. The objectives of the study were to evaluate natural inexpensive raw laterite (RL) and kaolinite (RK) for their potential use as As sorbents and to understand the As sorption on laterite and kaolinite by employing sorption and kinetic models. Raw laterite and RK were tested for EC, pH, XRF and CEC as basic parameters. Batch sorption and kinetic experiments data were fitted in the sorption (Langmuir and Freundlich) model and kinetic (pseudo-first and pseudo-second order) reaction equations, respectively. Morphological and structural changes were observed in RL and RK samples before and after As saturation by employing FTIR and SEM. The major constituent in RL was Fe and Al oxides while in RK major oxides were silica and Al. The Freundlich sorption model well explained the experimental data, indicating a greater sorption capacity of RL on a hetero-layered surface compared to RK. The kinetic reaction equations showed that equilibrium was achieved after a contact time of 240 min and the adsorption was chemisorption in nature. The RL and RK were found to be effective sorbents for As removal, however, RL showed maximum As adsorption and thus superior in comparison with RK. Structural and morphological characterization reveals the role of Fe and Al oxides in the case of RL, and Al oxides in the case of RK, in the adsorption of As. Hence this study concludes that these naturally occurring inexpensive resources can be used as sorbent agents for As-contaminated drinking water treatment.

Biochar/nano-zerovalent zinc-based materials for arsenic removal from contaminated water

In this study, we explored the potential of a newly prepared nano-zero valent zinc (nZVZn), biochar (BC)/nZVZn and BC/hydroxyapatite-alginate (BC/HA-alginate) composites for the removal of inorganic As species from water. Relatively, higher percentage removal of As(III) and As(V) was obtained by nZVZn at pH 3.4 (96% and 94%, respectively) compared to BC/nZVZn (90% and 88%) and BC/HA-alginate (88% and 80%) at pH 7.2. Freundlich model provided the best fit (R 2 = up to 0.98) for As(III) and As(V) sorption data of all the sorbents, notably for nZVZn. The pseudo-second order model well-described kinetics of As(III) and As(V) (R2 = 0.99) sorption on all the sorbents. The desorption experiments demonstrated that the As removal efficiency, up to the third sorption/desorption cycle, was in the order of nZVZn ∼ BC/HA-alginate (88%) > BC/nZVZn (84%). The Fourier transform infrared spectroscopy depicted that the –OH, –COOH, Zn–O and Zn–OH surface functional groups were responsible for the sorption of As(III) or As(V) on the sorbents investigated here. This study highlights that removal of As species from water by BC/nZVZn composite can be compared with nZVZn, suggesting that integrating BC with nZVZn could efficiently remove As from As-contaminated drinking water.

Mulberry leaves juice attenuates arsenic-induced neurobehavioral and hepatic disorders in mice.

Arsenic (As) poisoning has caused an environmental catastrophe in Bangladesh as millions of people are exposed to As-contaminated drinking water. Chronic As-exposure causes depression, memory impairment, and liver injury in experimental animals. This study was carried out to assess the protective effect of mulberry leaves juice (Mul) against As-induced neurobehavioral and hepatic dysfunctions in Swiss albino mice. As-exposed mice spent significantly reduced time in open arms and increased time spent in closed arms in the elevated plus maze (EPM) test, whereas they took significantly longer time to find the hidden platform in the Morris water maze (MWM) test and spent significantly less time in the desired quadrant when compared to the control mice. A significant reduction in serum BChE activity, an indicator of As-induced neurotoxicity-associated behavioral changes, was noted in As-exposed mice compared to control mice. Supplementation of Mul to As-exposed mice significantly increased serum BChE activity, increased the time spent in open arms and reduced time latency to find the hidden platform, and stayed more time in the target quadrant in EPM and MWM tests, respectively, compared to As-exposed-only mice. Also, a significantly reduced activity of BChE, AChE, SOD, and GSH in brain, and elevated ALP, AST, and ALT activities in serum were noted in As-exposed mice when compared to control mice. Mul supplementation significantly restored the activity of these enzymes and also recovered As-induced alterations in hepatic tissue in As-exposed mice. In conclusion, this study suggested that mulberry leaves juice attenuates As-induced neurobehavioral and hepatic dysfunction in mice.

Treatment of As-contaminated drinking water using a nano zero-valent iron/copper slag nanocomposite

Arsenite (As(ΙΙΙ)) is one of the most toxic contaminants in surface and underground waters that needs to be removed from aquatic environments as it has harmful effects on human health and other living organisms. In this study, copper slag supported nanoscale zero-valent iron (nZVI/copper slag) adsorbent is used to reduce the concentration of As(ΙΙΙ) from an aqueous environment up to a permissible level. nZVI/copper slag adsorbent was prepared using Fe3+ reduction by BH−. FE-SEM, EDX, XRD, FTIR, BET, VSM, and Zeta potential were utilized for characterization of the adsorbent synthesis. In this study, effective parameters on the As(ΙΙΙ) removal were made into a function of initial concentration, adsorbent dosage, and pH of the solution at a constant time of 5 min using Design-Expert software. The results of experiments showed that only 7.9 g/L of nZVI/copper slag adsorbent in 5 min and pH of 5.4 can remove >99 % of As(ΙΙΙ) with the initial concentration of 20 mg/L in aqueous solution. Among different isotherms, the Langmuir model with a maximum adsorption capacity of 4.27 mg/g could describe As(ΙΙΙ) adsorption model. In addition, it was found that adsorption followed the pseudo-second order kinetics model. The amount of iron (Fe) leached from the adsorbent surface of nZVI/copper slag has been significantly reduced by using pure copper slag as a substrate in 3 consecutive cycles. Furthermore, nZVI/copper slag adsorbent can be separated from aqueous media by applying an external magnetic field due to its magnetic properties and high weight of pure copper slag.

Arsenic-contaminated drinking water and cholangiocarcinoma.

Cholangiocarcinoma (CCA) is an aggressive tumor occurring in bile ducts and associated with dismal outcomes. It can be classified according to anatomical location as intrahepatic cholangiocarcinoma (ICC) or extrahepatic cholangiocarcinoma (ECC). Although some risk factors have been identified, our understanding of these tumors remains limited. Arsenic (As) is a prevalent toxicant with established associations with bladder, skin and lung cancers while pilot data on its potential carcinogenic role on digestive tumors are emerging. This ecological study aimed to investigate the association between exposure to As-contaminated drinking water and CCA. Analyses were conducted for the US, Taiwan and India due to the quality of publicly available datasets including small area-level information. Statistics included coefficient correlations analyses as well as univariate and multivariate linear regressions. In the US, no correlation was observed between As and CCA. In Taiwan, correlations were identified for ICC in men (Spearman = 0.55, P = 0.01) and women (Spearman = 0.67, P < 0.01), as well as for ECC in men (Spearman = 0.62, P < 0.01). In India, counties with As level of at least 50 µg/L showed higher incidences of ECC in men ( R2 = 0.26, P = 0.01) and women ( R2 = 0.31, P < 0.01). These findings highlighted a potential carcinogenic impact of As in drinking water on bile duct cancers, paving the way for future studies aiming to replicate this association with individual data as well as its clinical and ecological implications.

Nutrition, one-carbon metabolism and arsenic methylation in Bangladeshi adolescents

BackgroundOver 57 million people in Bangladesh are chronically exposed to arsenic-contaminated drinking water. Ingested inorganic arsenic (InAs) undergoes hepatic methylation generating monomethyl- (MMAs) and dimethyl- (DMAs) arsenic species in a process that facilitates urinary As (uAs) elimination. One-carbon metabolism (OCM), a biochemical pathway that is influenced by folate and vitamin B12, facilitates the methylation of As. OCM also supports nucleotide and amino acid synthesis, particularly during periods of rapid growth such as adolescence. While folate supplementation increases As methylation and lowers blood As (bAs) in adults, little data is available for adolescents. ObjectivesTo examine the associations between OCM-related micronutrients and As methylation in Bangladeshi adolescents chronically exposed to As-contaminated drinking water. MethodsWe conducted a cross-sectional study of 679 Bangladeshi adolescents, including 320 boys and 359 girls aged 14–16 years. Nutritional status was assessed by red blood cell (RBC) folate, plasma folate, plasma B12 and homocysteine (Hcys). Arsenic-related outcomes included blood arsenic (bAs), urinary arsenic (uAs), and urinary arsenic metabolites expressed as a percentage of total urinary As: %InAs, %MMAs, %DMAs. ResultsBoys had significantly lower B12, higher Hcys, higher bAs, higher uAs, higher %MMAs, and a trend toward lower RBC folate compared to girls. Therefore, regression analyses controlling for water As and BMI were sex stratified. Among girls, RBC folate was inversely associated with bAs, plasma B12 was inversely associated with uAs, and plasma Hcys was inversely associated with %MMA. Among boys, plasma folate was inversely associated with %InAs and positively associated with %DMA, RBC folate was inversely associated with %InAs and positively associated with %MMA, while Hcys was positively associated with %InAs. ConclusionsThese findings suggest that associations between OCM nutritional status, bAs, and distribution of As metabolites in adolescents are similar to previously reported observations in adults and in children. The As methylation findings are statistically significant among boys but not among girls; this may be related to estrogen which more strongly influences OCM in females. The inverse association between Hcys and %MMA in girls is somewhat unexpected given that Hcys is known to be an indicator of impaired OCM and low folate/B12 in adults. Overall, these results indicate that the associations between OCM-related micronutrients and arsenic methylation in adolescents are generally similar to prior findings in adults, though these associations may differ by sex. Additionally, these findings suggest that more investigation into the role of Hcys in adolescent physiology is needed, perhaps particularly for girls. Additional studies are needed to evaluate the impact of OCM and As methylation on As-related adverse health outcomes (such as cancer and cardiovascular disease) in people exposed to As during adolescence.

Microbe-mediated management of arsenic contamination: current status and future prospects

Arsenic (As) contamination is an issue recognized as a serious risk throughout the world. Among several oxidation states of As existing in the environment, like arsenate [As (V)], arsenite [As (III)], elemental As [As (0)] and arsenide, toxicity of As (III) is 25–60 times more than As (V). Over the period the accumulation of As in the environment has increased several folds thereby contaminating the soil and resulting in biomagnification affecting the food chain. As-contaminated drinking water and its accumulation in food leads to its long term exposure and is a threat not only to human health but to animals and plants also. Toxicity of As in animals and humans via food warrants in developing appropriate regulatory measures as well as remediation of As contaminated environments by feasible technologies. Commonly in such cases As removal is done by the chemical based conventional techniques such as precipitation, oxidation and reduction as well as ion exchange, filtration and reverse osmosis. Such techniques are not only costly but also have drawbacks on account of removal accuracy and are not environment-friendly as they result in secondary pollution caused by chemicals used in the process. There is need for development of affordable, environment friendly and sustainable options of remediation in which microorganisms can provide an aid. Capability of microorganisms for transformation of As into various oxidation states with different solubility, mobility and toxicity can be used in As bioremediation strategies. The biological metabolic properties of the microbes which make them able to survive in high exposure of As need to be explored and exploited in developing cost effective and sustainable large-scale As remediation bio-systems.

Compositional and health risk assessment of drinking water from health facilities of District Vehari, Pakistan.

Arsenic (As) is a potentially toxic and carcinogenic metalloid. It has gained considerable attention owing to its high ecotoxic nature. High As contamination of groundwater in scattered areas is the current status of Pakistan. A number of assessments exist for the As contamination of the drinking water in District Vehari, Pakistan. However, there is scarcity of data about As contents in drinking water of health facilities and healthcare centers in District Vehari. The current study, therefore, was carried out to assess As concentration and associated health risk in the drinking water of three health facilities (district head quarter, rural health center and basic health unit) of District Vehari. In total, 75 drinking water samples were collected and examined for As contents in addition to physicochemical characteristics such as electrical conductivity, pH, total soluble salts, chloride, carbonates, bicarbonates, fluoride, nitrate, nitrite, calcium, magnesium and iron. Results indicated that the groundwater samples are not fully fit for drinking purposes with respect to several parameters, especially the alarming levels of As. It was found that 52% of drinking water samples of Vehari have As concentration greater than WHO permissible limit (10µg/L) and 17% have As concentration greater than Pak-EPA permissible limit (50µg/L). The risk assessment parameters (average daily dose, hazard quotient and carcinogenic risk) showed possible carcinogenic and non-carcinogenic risks associated with ingestion of As-contaminated drinking water in the healthcare facilities. Based on the results of the present study, it is anticipated that hospitals and health centers in Vehari are in need of safe drinking water. The implementation of national/international standards for drinking water in healthcare facilities is a necessary measure to improve the services and increase local access to safe drinking water. The same may be applied to other public offices and organizations such as educational institutes and district government offices.

Adsorption behavior and mechanism of arsenic on mesoporous silica modified by iron-manganese binary oxide (FeMnOx/SBA-15) from aqueous systems

Iron-manganese binary oxides (FeMnOx) can remove contaminants from aqueous solutions with high efficiency, and mesoporous silica (SBA-15) is widely used as a supporting material due to its large specific surface area and good stability. In this study, SBA-15 was used to support FeMnOx in the synthesis of a novel arsenic (As) adsorbent (FeMnOx/SBA-15), and its characteristics under different reaction conditions, such as pH, temperature, presence of competing ions, and humic acid, were tested. The results showed that the contaminant adsorption efficiency of the novel adsorbent was better than that of bare FeMnOx, as the addition of SBA-15 decreased the agglomeration effect of FeMnOx. Additionally, FeMnOx/SBA-15 underwent calcination to further enhance its performance. The state of iron and manganese in FeMnOx/SBA-15 and the corresponding arsenic removal efficiency were improved by calcination at 350 °C with an FeMnOx/SBA-15 mass fraction of approximately 45%. Almost 90% of As (50 mL, 5.0 mg L−1) could be removed by 0.2 g L−1 of FeMnOx/SBA-15 (mass ratio of 45% and calcination temperature of 350 °C). The FeMnOx/SBA-15 could regenerate and still be used after four consecutive cycles. The high As sorption capacity, ability to regenerate, and reusability of FeMnOx/SBA-15 confirmed that this adsorbent is promising for treating As-contaminated drinking water.

Risk Assessment of Arsenic in Wheat and Maize Grown in Organic Matter Amended Soils of Indo-Gangetic Plain of Bihar, India

ABSTRACT Recent outbreak of geogenic arsenic (As) contamination in the Gangetic Delta basin of Bihar drew due attention of researchers as prolonged consumption of As-contaminated drinking water and food leads to arsenicosis, with the symptoms of pigmentation and keratosis in human. Although some information on As content in rice grain grown on contaminated soil is available specific to some areas of Bihar, practically no such information is available on wheat and maize crops. The present field experiment was conducted to evaluate the efficacy of organic amendments in reducing the availability of As in contaminated soils, followed by its uptake by wheat and maize. Accumulation of total As in wheat and maize grains varied from 0.02 to 0.11 mg kg−1 and from 0.23 to 0.29 mg kg−1, respectively, whereas available As in post-harvest soil varied from 1.07 to 1.33 mg kg−1 for wheat and from 1.10 to 1.24 mg kg−1 for maize. The organic amendments reduced the As accumulation in wheat grain to the extent of 84% (sugarcane bagasse (SB)), 50% (rice straw) and 40% (paddy husk (PH)) compared with control. Similarly, As content in maize grain was the lowest in SB-treated soil followed by rice straw and PH. Solubility-free ion activity model, based on pH, organic carbon and Olsen extractable As, was effective in predicting the As uptake by wheat and maize grains to the extent of 75% and 87%, respectively. Impact of organics in reducing health hazard for intake of As through consumption of wheat and maize grains grown on contaminated soil was also reflected in the values of the corresponding hazard quotient (HQ).

Assessment of arsenic exposure by drinking well water and associated carcinogenic risk in peri-urban areas of Vehari, Pakistan.

Arsenic (As) is a highly toxic and carcinogenic element. It has received considerable consideration worldwide in recent years due to its highest toxicity to human, and currently, high concentrations observed in the groundwater. Some recent media and research reports also highlighted possible As contamination of groundwater systems in Pakistan. However, there is a scarcity of data about As contents in groundwater in different areas/regions of the country. Consequently, the current study estimated the As concentration in the groundwater used for drinking purpose in 15 peri-urban sites of district Vehari, Pakistan. In total, 127 groundwater samples were collected and examined for As contents in addition to physicochemical characteristics such as temperature, electrical conductivity, pH, total soluble salts, chloride, carbonates, bicarbonates, sodium, potassium, lithium, calcium and barium. Results indicated that the groundwater samples were not fully fit for drinking purposes with several parameters, especially the alarming levels of As (mean As: 46.9µg/L). It was found that 83% groundwater samples of peri-urban sites in district Vehari have As concentration greater than WHO lower permissible limit (10µg/L). The risk assessment parameters (mean hazard quotient: 3.9 and mean cancer risk: 0.0018) also showed possible carcinogenic and non-carcinogenic risks associated with ingestion of As-contaminated groundwater at peri-urban sites. Based on the findings, it is anticipated that special monitoring and management of groundwater is necessary in the studied area in order to curtail the health risks associated with the use of As-contaminated drinking water. Moreover, appropriate remediation and removal of As from groundwater is also imperative for the study area before being used for drinking purpose to avoid As exposure and related risks to the local community.

Ingestion of Arsenic-Contaminated Drinking Water Leads to Health Risk and Traces in Human Biomarkers (Hair, Nails, Blood, and Urine), Pakistan

Human exposure to arsenic (As) is a global public health concern that frequently occurs through both dietary and non-dietary pathways. This is the first systematic field study that investigated the drinking water (n = 190) for concentrations of total As (AsT) and its inorganic species such as arsenate As(V) and arsenite As(III) and organic species including monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA) collected from Khyber Pakhtunkhwa, Pakistan. The concentrations of AsT surpassed (from 1.2- to 23-fold) the world health organization (WHO) drinking water guidelines in 28% samples collected from Dera Ismail Khan (D.I. Khan) and Lakki Marwat. Results revealed that among As species, As(III) showed the highest concentration (116 µg L−1) in drinking water samples. In addition, the results revealed that the chronic or non-cancer risk (HQ > 1) and cancer risk (1.0E-03 to 1.0E-06) values were above their respective safe limits. Further, As species concentrations were determined in consumer biomarkers (n = 60) such as blood (red blood cells and plasma), hair, nails, and urine. The highest AsT (170 µg kg−1) accumulation was observed in hair samples collected from the resident of D.I. Khan District. The study revealed that high As-contaminated drinking water led to its accumulation in human body that could threaten the exposed population with hazardous chronic and cancer diseases.

Exploring the arsenic removal potential of various biosorbents from water

Globally, contamination of groundwater with toxic arsenic (As) is an environmental and public health issue given to its carcinogenic properties, thereby threatening millions of people relying on drinking As-contaminated well water. Here, we explored the efficiency of various biosorbents (egg shell, java plum seed, water chestnut shell, corn cob, tea waste and pomegranate peel) for arsenate (As(V)) and arsenite (As(III)) removal from As-contaminated water. Significantly, egg shell and java plum seed displayed the greatest As(III) elimination (78–87%) at 7 pH followed by water chestnut shell (75%), corn cob (67%), tea waste (74%) and pomegranate peel (65%). In contrast, 71% and 67% of As(V) was removed at pH 4.1 and 5.3 by egg shell and java plum seed, respectively. The maximum As(V) and As(III) sorption by all the biosorbents was obtained, notably for egg shell and java plum seed, after 2 h contact time. Langmuir isotherm and pseudo-second order models best fitted the sorption data for both forms of As. The –OH, –COOH, –NH2 and sulfur-bearing surface functional groups were possibly involved for As(III) and As(V) removal by biosorbents. The scanning electron microscopy combined with the energy dispersive X-ray spectroscopy (SEM-EDX) analysis showed that the heterogeneous surface of biosorbents, possessing rough and irregular areas, could have led to As sorption. Both As(V) and As(III) were successfully desorbed (up to 97%) from the biosorbents in four sorption/desorption (regeneration) cycles. This pilot-scale study highlights that egg shell and java plum seed have the greatest ability to remove both As species from As-contaminated drinking water. Importantly, these findings provide insights to develop an inexpensive, effective and sustainable filtration technology for the treatment of As in drinking water, particularly in developing countries like Pakistan.

Hydrogeochemical controls on mobilization of arsenic and associated health risk in Nagaon district of the central Brahmaputra Plain, India.

In recent years, elevated concentration of arsenic (As) in groundwater in the northeastern states of India has become a major cause of concern. Since many regions of the Brahmaputra plains are reported with groundwater As contamination, an attempt was made to study the As contamination and factors governing its release in the Nagaon district in Brahmaputra floodplain, based on various water types, relation of As with other major ions and with various depth profiles. The origin of groundwater mineralization and the processes responsible for As enrichment in groundwater was determined by calculating saturation index using PHREEQC code. Multivariate statistical analysis was carried out for identification of As-releasing mechanism based on rock-water interaction. Principle component analysis of physicochemical parameters revealed the association of As with SiO2 and Cl- in pre-monsoon and the fact that alkaline condition favors release of As. The relation between As and Fe shows that reductive dissolution of solid Fe oxide and hydroxide phases could be the source of As in Nagaon district. The result of hierarchical cluster analysis indicates that As release could also be associated with the agrochemicals application. Health risk assessment revealed that children are more susceptible to carcinogenic as well as non-carcinogenic health impact with consumption of As-contaminated drinking water. The male population is more susceptible to cancer as compared to females as the average water consumption is higher in case of male. Overall, the study highlights the health risk assessment is a matter of chief concern in this study as the younger generation are at higher risk.

Arsenic Uptake and Translocation in Plants.

Arsenic (As) is a highly toxic metalloid that is classified as a non-threshold class-1 carcinogen. Millions of people worldwide suffer from As toxicity due to the intake of As-contaminated drinking water and food. Reducing the As concentration in drinking water and food is thus of critical importance. Phytoremediation of soil contaminated with As and the reduction of As contamination in food depend on a detailed understanding of As uptake and transport in plants. As transporters play essential roles in As uptake, translocation and accumulation in plant cells. In this review, we summarize the current understanding of As transport in plants, with an emphasis on As uptake, mechanisms of As resistance and the long-distance translocation of As, especially the accumulation of As in grains through phloem-mediated transport.

A dose-response study of arsenic exposure and markers of oxidative damage in Bangladesh.

To evaluate the dose-response relationship between arsenic (As) exposure and markers of oxidative damage in Bangladeshi adults. We recruited 378 participants drinking water from wells assigned to five water As exposure categories; the distribution of subjects was as follows: (1) less than 10 μg/L (n=76); (2) 10 to 100 μg/L (n=104); (3) 101 to 200 μg/L (n=86); (4) 201 to 300 μg/L (n=67); and (5) more than 300 μg/L (n=45). Arsenic concentrations were measured in well water, as well as in urine and blood. Urinary 8-oxo-2'-deoxyguanosine and plasma protein carbonyls were measured to assess oxidative damage. None of our measures of As exposure were significantly associated with protein carbonyl or 8-oxo-2'-deoxyguanosine levels. We found no evidence to support a significant relationship between long-term exposure to As-contaminated drinking water and biomarkers of oxidative damage among Bangladeshi adults.

Arsenic Exposure to Dairy Cows in Bangladesh

Food-chain contamination by arsenic (As) is a newly uncovered disaster. Effects of As-contaminated drinking water and paddy straw on the excretion of As through milk, urine, and dung of dairy cows (n = 240) were studied in As-prone areas of Bangladesh. Mean (±SEM) total As (inorganic plus organic) concentration in drinking water, paddy straw [dry weight dw)], cow's urine (specific gravity adjusted to 1.035), dung (dw), and milk (wet weight) were 89.6 ± 6.5 μg/l, 1,114.4 ± 57.3 μg/kg, 123.6 ± 7.6 μg/l, 1,693.0 ± 65.1 μg/kg, and 26.2 ± 2.8 μg/l, respectively. Significantly (p < 0.01) greater As was in Boro straw (1,386.9 ± 71.8 μg/kg) than Aus (702.4 ± 67.1 μg/kg) and Aman (431.7 ± 28.8 μg/kg) straw and in straw irrigated with shallow (1,697.3 ± 81.9 μg/kg) than deep well water (583.6 ± 62.7 μg/kg) and surface water (511.8 ± 30.0 μg/kg). Significant (p < 0.01) positive correlations were found between As contents of cow's urine and drinking water (r = 0.92) as well as cow dung and straw (r = 0.82). Concentrations of As in cow urine, dung, and milk were increased with the relative increment of As in drinking water and/or straw. These results provide evidence that dairy cows excrete ingested As mainly through urine and dung; thus, As biotransformation through milk remains low. This low concentration of As in milk may be of concern when humans are exposed to multiple sources of As simultaneously. Moreover, As in cow dung could be an environmental issue in Bangladesh.

Microprobe XRF Mapping and XAS Investigations of the Intracellular Metabolism of Arsenic for Understanding Arsenic-Induced Toxicity

Arsenic (As) is responsible for mass-poisonings worldwide following the ingestion of As-contaminated drinking water. Importantly, however, As toxicity is exploited in the antileukemia drug, Trisenox (As2O3), which successfully cures 65-80% of patients suffering relapsed acute promyelocytic leukemia. In an effort to determine the intracellular organelle and biomolecular targets of As, microprobe X-ray fluorescence (XRF) and X-ray absorption spectroscopy (XAS) analyses were performed on HepG2 cells following their exposure to high doses of arsenite (1 mM) or arsenate (20 mM). Microprobe XRF elemental mapping of thin-sectioned cells showed As accumulation in the euchromatin region of the cell nucleus (following arsenite exposure) synonymous with As targeting of DNA or proteins involved in DNA transcription. X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) analysis of arsenite-treated cells, however, showed the predominance of an As tris-sulfur species, providing increased credence to As interactions with nuclear proteins as a key factor in As-induced toxicity.

Human Health Effects From Chronic Arsenic Poisoning–A Review

The ill effects of human exposure to arsenic (As) have recently been reevaluated by government agencies around the world. This has lead to a lowering of As guidelines in drinking water, with Canada decreasing the maximum allowable level from 50 to 25 μg/L and the U.S. from 50 to 10 μg/L. Canada is currently contemplating a further decrease to 5 μg/L. The reason for these regulatory changes is the realization that As can cause deleterious effects at lower concentrations than was previously thought. There is a strong relationship between chronic ingestion of As and deleterious human health effects and here we provide an overview of some of the major effects documented in the scientific literature. As regulatory levels of As have been decreased, an increasing number of water supplies will now require removal of As before the water can be used for human consumption. While As exposure can occur from food, air and water, all major chronic As poisonings have stemmed from water and this is usually the predominant exposure route. Exposure to As leads to an accumulation of As in tissues such as skin, hair and nails, resulting in various clinical symptoms such as hyperpigmentation and keratosis. There is also an increased risk of skin, internal organ, and lung cancers. Cardiovascular disease and neuropathy have also been linked to As consumption. Verbal IQ and long term memory can also be affected, and As can suppress hormone regulation and hormone mediated gene transcription. Increases in fetal loss and premature delivery, and decreased birth weights of infants, can occur even at low (<10 μg/L) exposure levels. Malnourished people have been shown to be more predisposed to As-related skin lesions. A large percentage of the population (30–40%) that is using As-contaminated drinking water can have elevated As levels in urine, hair and nails, while showing no noticeable clinical symptoms, such as skin lesions. It is therefore important to carry out clinical tests of As exposure. Factors combining to increase/decrease the ill effects of As include duration and magnitude of As exposure, source of As exposure, nutrition, age and general health status. Analytical determinations of As poisoning can be made by examining As levels in urine, hair and toenails. Communities and individuals relying on groundwater sources for drinking water need to measure As levels to ensure that their supplies are safe. Communities with water As levels greater than 5 μg/L should consider a program to document As levels in the population.